Data storage library status monitoring

ABSTRACT

Library system health is monitored and displayed based on the location of equipment within the library relative to track layout. Robotic devices travel on rails within the data storage library accessing data storage devices such as cartridges, cassettes, media packages, media access equipment, identification devices, access ports and the like. The rails are divided into a plurality of rail segments. A database holds information about each rail segment. The database is updated based on use of each rail segment by the robotic devices. Data is generated and displayed to describe the use of each rail segment.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the detection of trackanomalies in data storage libraries.

2. Background Art

Current automated libraries for tape cartridges typically include arraysof multiple storage cells housing the tape cartridges, as well asmultiple media drives. Multiple automated robotic devices may be used tomove tape cartridges between the various storage cells and media driveswithin a library.

The use of multiple robotic devices in automated tape cartridgelibraries raises various problems concerning the distribution of powerto such robotic devices. More particularly, robotic devices used inautomated tape cartridge libraries require power for operation thereof.In prior art automated tape cartridge libraries, the movement of therobotic devices is restricted by wire cable connections used forproviding such power. That is, such cabling can prevent the roboticdevices from crossing paths, or from continuous movement in onedirection around the library without the necessity of ultimatelyreversing direction.

Power cabling can be eliminated through the use of conductors, or powerstrips, running along tracks which support the robotic devices. Brusheson the robotic devices contact the conductors to supply power to therobotic devices. Alternatively, brushes may be part of a pickup assemblyfor supplying power to the robotic devices. For example, wheels maycontact the conductors with brushes contacting the wheels.

Tracks, conductors, robotic devices, media access devices, elevators,controllers, monitors and various other pieces of equipment within thelibrary may cease to function properly through use, age, improperinstallation, physical damage, and the like. What is needed is tomaintain the status of these pieces of equipment and display this statusto library operators.

SUMMARY OF THE INVENTION

Library system health is monitored and displayed based on the locationof equipment within the library relative to track layout.

A method of monitoring status in a data storage library is provided.Robotic devices travel on rails within the data storage libraryaccessing data storage devices such as cartridges, cassettes, mediapackages, media access equipment, identification devices, access portsand the like. The rails are divided into a plurality of rail segments. Adatabase holds information about each rail segment. The database isupdated based on use of each rail segment by the robotic devices. Datais generated to describe the use of each rail segment.

In an embodiment of the present invention, a display having a pluralityof display elements is generated. Each display element represents onerail segment. Each display element is positioned relative to otherdisplay elements in the display to reflect positioning of correspondingrail segments within the data storage library. The display is updatedbased on data generated to describe the use of each rail segment.

In other embodiments of the present invention, generating data includesone or more of determining a mechanical condition of each rail segment,determining an electrical condition of each rail segment, determiningdistance of robotic device travel along each rail segment, determiningease of travel of robotic devices along each rail segment, and the like.

A data storage library is also provided. Storage locations for holdingdata storage media are disposed within the library. At least one railprovides access to storage locations. Each rail is logically dividedinto at least one rail segment. At least one robotic device is mountedto travel along each rail to access storage media held in the storagelocations. A database holds operational status information about thedata storage library arranged according to rail segment. A graphicaldisplay displays the condition of each rail segment as a graphicalelement. Each graphical element is positioned on the display relative toother graphical elements so as to have the same logical relationship asthe position of the rail segment corresponding to the graphical elementrelative to rail segments corresponding to other displayed graphicalelements. Control logic monitors the operating condition of each railsegment, records the operating condition of each rail segment in thedatabase, determines an operating fault with any rail segment, andupdates the display based on the determined operating fault.

In an embodiment of the present invention, the graphical displaydisplays the location of each robotic device.

In another embodiment of the present invention, the graphical displaydisplays the operational status of at least one data storage accessdevice.

A method of diagnosing the condition of an automated data storagelibrary is also provided. The location of each robotic device operatingwithin the library is determined. A rail segment supporting each roboticdevice is determined based on the location. Usage information of eachdetermined rail segment is accumulated and recorded in association witheach rail segment. Usage alarms are determined based on the accumulatedusage information.

A method of displaying the status of an automated data storage libraryis also provided. Each rail upon which robotic devices travel is dividedinto rail segments. A request to display at least one rail is received.Graphical symbols are generated for rail segments comprising eachrequested rail. The rail segment graphical symbols are displayed on adisplay screen so as to create a logical representation of eachrequested rail. An indication of the status of each rail segmentcomprising each requested rail is displayed on the display screen.

In an embodiment of the present invention, once a problem has occurredon a rail segment, the rail segment graphical symbols for the railincluding the rail segment are automatically displayed. The rail segmentgraphical symbol corresponding to the rail segment with the operationalproblem is highlighted.

A method of monitoring status of an automated data storage library isprovided. Operation of each robotic device within the data storagelibrary is correlated to a guide rail segment currently supporting therobotic device. Reliability statistics generated from robotic deviceoperation are mapped to each guide rail segment. The reliabilitystatistics may be displayed in association with a display of the guiderail segment with which the reliability statistic is mapped.

The above features, and other features and advantages of the presentinvention are readily apparent from the following detailed descriptionsthereof when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a robotic device for use in an automatedtape cartridge library having brush and strip power distribution;

FIGS. 2a and 2 b are partial cross-sectional views of a robotic devicefor use in an automated tape cartridge library having brush and strippower distribution;

FIG. 3a is a simplified block diagram of a robotic device for use in anautomated tape cartridge library;

FIG. 3b is a simplified a block diagram of a robotic device for use inan automated tape cartridge library having brush and strip powerdistribution;

FIGS. 4a and 4 b are simplified overhead block diagrams of a power stripand robotic device with conductive brushes for use in an automated tapecartridge libraries that may be used with the present invention;

FIGS. 4c and 4 d are simplified electrical schematics depicting powersupply redundancy schemes that may be used with the present invention;

FIG. 5 is a perspective view of a robotic device for use in an automatedtape cartridge library having brush and wheel power distribution thatmay be used with the present invention;

FIG. 6 a more detailed perspective view of a robotic device for use inan automated tape cartridge library having brush and wheel powerdistribution that may be used with the present invention;

FIG. 7 is another more detailed perspective view of a robotic device foruse in an automated tape cartridge library having brush and wheel powerdistribution that may be used with the present invention;

FIGS. 8a and 8 b are side and cross-sectional views, respectively, of abrush and wheel mechanism for power distribution to a robotic device inan automated tape cartridge library that may be used with the presentinvention;

FIG. 9 is an exploded perspective view of power strip and guide railjoint for use in an automated tape cartridge library that may be usedwith the present invention;

FIG. 10 is a perspective view of a power strip joint for use in anautomated tape cartridge library that may be used with the presentinvention;

FIGS. 11a and 11 b are additional perspective views of a power stripjoint for use in an automated tape cartridge library that may be usedwith the present invention;

FIGS. 12a and 12 b are perspective views of guide rail sections for usein an automated tape cartridge library having brush and strip powerdistribution;

FIGS. 12c-g are cross-sectional and side views of a power strip andguide rail assembly for use in an automated tape cartridge library;

FIG. 13 is a simplified block diagram illustrating distribution ofcommunication signals to and from robotic devices for use in anautomated tape cartridge library according to an embodiment of thepresent invention;

FIG. 14 is a cross-sectional view of a power strip and conductivebrushes for use in an automated tape cartridge library;

FIG. 15 is a top view of a power strip for use in an automated tapecartridge library;

FIGS. 16a and 16 b are a cross-sectional view and a simplifiedelectrical schematic, respectively, of a power strip for use in anautomated tape cartridge library;

FIG. 17 is a simplified electrical schematic diagram illustrating atermination scheme for a line in a power strip or rail communicationsystem;

FIG. 18 is a schematic diagram illustrating a system for detecting brushfailure;

FIGS. 19a-19 d are schematic diagrams illustrating circuitry fordetecting brush failures or track defects;

FIG. 20 is a schematic diagram illustrating power strip fault detectionthrough current sensing by the robotic device;

FIG. 21 is a schematic diagram illustrating power strip fault detectionthrough voltage sensing by the robotic device;

FIG. 22 is a schematic diagram illustrating power strip fault detectionthrough impedance sensing by the robotic device;

FIG. 23 is a schematic diagram illustrating track fault detection byimpedance measurement;

FIG. 24 is a schematic diagram illustrating embodiments of track faultdetection by signal transmission;

FIG. 25 is a schematic diagram illustrating an alternative embodiment oftrack fault detection by signal transmission;

FIG. 26 is a schematic diagram illustrating track fault detection with aplurality of signal transmitters;

FIG. 27 is a schematic diagram illustrating track fault detection with aplurality of signal receivers;

FIG. 28 is a schematic diagram illustrating rail anomaly recovery;

FIG. 29 is an illustration of a linear data storage library with agraphical display;

FIG. 30 is an illustration of a data storage library with curved tracks;

FIG. 31 is an illustration of a curved track data storage library with agraphical display;

FIG. 32 illustrates a graphical display for a multi-track data storagelibrary; and

FIG. 33 is a block diagram illustrating a data storage system withtrack-based status monitoring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2a-b show perspective and cross-sectional views,respectively, of a robotic device for use in an automated tape cartridgelibrary having brush and strip power distribution. As seen therein, amoveable robotic device (20), which may be referred to as a “handbot” or“picker,” is supported by a guide structure or rail (2) preferablyhaving an integrated power strip or conductor (1). Guide rail (2) and/orpower strip (1) may also be referred to as a track. Power strip (1) is asubstantially planar elongated member, preferably comprisingback-to-back conductive surfaces (1A, 1B), preferably copper, separatedby a dielectric (preferably FR4) in a sandwich-like configuration. Powerstrip (1) may be a printed circuit board wherein copper conductors arelaminated, glued or etched onto a substrate material. Alternatively,power strip (1) may comprise copper foil tape glued or laminated ontoplastic material, or copper inserts molded into a moldable plasticmaterial. Any other methods of construction or configurations known tothose of ordinary skill may also be used.

Robotic device (20) includes brush contacts (6) for providing power torobotic device (20). In that regard, the back-to-back conductivesurfaces (1A, 1B) of power strip (1) are oppositely charged. An upperbrush (6A) in contact with one conductive surface (I A), in conjunctionwith a corresponding lower brush (6B) in contact with the oppositeconductive surface (1B) thereby supply power to the robotic device (20).Brushes (6) are contained in housing assembly (7) and, to ensure thatcontact between brushes (6) and power strip (1) is maintained, brushes(6) are spring loaded (8). Multiple or redundant pairs of such upper andlower brushes (6) may be provided, and may be spring loaded (8)independently, to improve robustness and reliability in the event of abrush failure, momentary loss of contact at one or more brushes due toany track irregularities, including seams or joints therein, or voltageirregularities between adjacent power strips (1). Moreover, brushes (6)may have a circular cross-section, such as is provided by a cylindricalshaped brush (6), as these are better able to traverse a joint or seam(38) in the power strip (1), which may more readily impede or catch asquare shaped brush. In that regard, as best seen in FIGS. 2a and 2 b,brushes (6) may have a substantially flat surface for contacting theconductive surfaces (1A, 1B) of power strip (1).

Power supplied to robotic device (20) through power strip (1) andbrushes (6) powers a motor (not shown) in robotic device (20), which inturn drives a belt and gear system (22). Guide rails (2) includes teeth(24) which cooperate with belt and gear system (22) to permit roboticdevice (20) to move back and forth along guide rails (2) via guidewheels (26). In that regard, it should be noted that power strip (1)preferably provides DC power to robotic device (20). As seen in FIG. 1,robotic device (20) may thereby gain access to tape cartridges stored inlibrary cells (28) located along guide rail (2). It should also be notedthat while only a single robotic device (20) is depicted, power strip(1) is preferably suitable, according to any fashion known in the art,to provide power to multiple robotic devices. In that regard, eachrobotic device (20) is suitably equipped with a circuit breaker (notshown) in any fashion known in the art in order to isolate the roboticdevice (20) from the power strip (1) in the event that the roboticdevice short circuits. In such a manner, the failure of the entire powerstrip (I) is prevented.

Referring now to FIG. 3a, a simplified block diagram of a robotic devicefor use in an automated tape cartridge library is shown. Robotic device(30) in an automated tape cartridge library has a pair of spaced apart,oppositely charged power rails (32). The robotic device (30) is providedwith a pair of brush contacts (34) for supplying power from two powerrails (32) to the robotic device (30), in order to allow movement of therobotic device (30). As seen in FIG. 3a, the large distance, x, betweena cooperating pair of brushes (34) creates uneven wear on the brushes(34) due to construction tolerances in the robotic device (30) and thetrack or power rails (32). Brushes (34) also causes uneven drag on therobotic device (30) by creating a moment load resulting from theseparation, x, between the brush (34) and power rail (32) frictionpoints.

FIG. 3b is a simplified a block diagram of a robotic device for use inan automated tape cartridge library having common rail brush and strippower distribution. Power is supplied to the robotic device (20) throughthe power strip (I) and brush (6) configuration described in connectionwith FIGS. 1 and 2a-b, thereby facilitating the elimination of the largeseparation between a pair of cooperating brushes (6A, 6B), and theaccompanying problems, and allowing for lower construction tolerancerequirements. The single rail construction, two-sided power strip (1)and brush (6) configuration also acts to reduce costs and provides for amore integrated assembly. As seen in FIG. 3b, an optional, non-poweredlower guide rail (36) may also be provided for robotic device (20). Itshould also be noted that the copper foil tape that may be used in theconstruction of the power strip (1) may be installed in the field duringthe assembly of the automated library. In such a fashion, it may bepossible to eliminate all electrical joints in power strip (1) by usinga continuous copper foil strip.

FIGS. 4a and 4 b are simplified overhead block diagrams of a power strip(1) and robotic device (20) with conductive brushes (6) for use in anautomated tape cartridge libraries according to the present invention.As seen in FIG. 4a, power strips (1) may be fed power from both endsthereof, or multiple sections of power strips may be fed from both ends.Robotic device (20) is preferably provided with multiple pairs ofcooperating brush contacts (6), only the top brushes in each cooperatingpair being visible in FIG. 4a. In that regard, with reference again toFIGS. 2a and 2 b, it should also be noted that brush pairs on each sideof power strip (1) are oriented so as to follow the same path. That is,a pair of brushes (6) contacting the same conductive surface (1A, 1B)are aligned so that both such brushes (6) contact the same part of theconductive surface (1A, 1B) as robotic device (20) moves in the library.Such a brush orientation facilitates the creation of a beneficial oxidelayer on the conductive surfaces (1A, 1B). As will be discussed ingreater detail below, such an oxide layer helps reduce both electricaland sliding resistance between the brushes and the conductive surfaces(1A, 1B).

Referring still to FIGS. 4a and 4 b, cooperating brush pairs arepreferably spaced apart on robotic device (20). Such spacing, as well asthe use of multiple cooperating brush pairs provides for greaterrobustness and freedom of movement for robotic device (20) in the eventof track irregularities, including unevenness or “dead” track sections.In that regard, as seen in FIG. 4a, a nonpowered or “dead” section (40)of power strip (1) will not necessarily prevent robotic device (20) fromtraversing the full extent of the power strip (1). That is, as therobotic device (20) moves across the dead track section (40), onecooperating pair of brushes always maintains contact with a poweredtrack section (42, 44). Similarly, as seen in FIG. 4b, power strip (1)may be fed power from a more centralized region thereof. As a result ofthe separation of cooperating pairs of brush contacts, robotic device(20) may be able to traverse longer distances than the length of powerstrip (1) onto and off of non-powered end-of-track sections (46, 48),provided at least one cooperating pair of brushes maintain contact withpowered track section (50). Moreover, in such a fashion, non-poweredtrack sections may be provided where a robotic device (20) may bedeliberately driven off power strip (1) and thereby powered down forservice.

FIGS. 4c and 4 d depict simplified electrical schematics of power supplyredundancy schemes. As seen in FIG. 4c, in a brush and strip powerdistribution system, failure of a power supply (150) or a break (152) inthe electrical continuity in a power strip (I) will cause a powerinterruption. Such an electrical discontinuity (152) in turn will resultin a loss of power to all of the robotic devices (20 i, 20 ii, 20 iii,20 iv) connected to the conductor. More specifically, such an electricalbreak (152) will result in the loss of power to those devices (20 iii,20 iv) located on the disconnected side (154) of the strip (1). As willbe described in greater detail below, a brush a strip power distributionsystem may be implemented using many interconnected segments or sectionsto create power strip (1). Each interconnect substantially increases thepossibility that power to part or all of the power strip (1) may beinterrupted.

The system shown in FIG. 4d provides for connecting two power supplies(150 i, 150 ii), rather than one, to power strip (1). The two powersupplies (150 i, 150 ii) are positioned at the two ends of power strip(1), and electrically connected to both ends of power strip (1). Thepower supplies (150 i, 150 ii) are preferably of the redundant/loadsharing type.

When both supplies (150 i, 150 ii) are active and functioning normally,they share the load created by robotic devices (20 i, 20 ii, 20 iii, 20iv) nearly equally. In the event, however, that one power supply (e.g.,150 i) fails, the remaining power supply (e.g., 150 ii) automaticallybegins to source power to all of the devices (20 i, 20 ii, 20 iii, 20iv) connected to the power strip (1). Moreover, in the event of anelectrical discontinuity or break (152) in the power strip (1), eachpower supply (150 i, 150 ii) will continue to deliver power to thedevices (20 i, 20 ii, 20 iii, 20 iv) located on that power supply's (150i, 150 ii) respective side of the break (152). Alternatively, as shownin dashed line fashion in FIG. 4c, single power supply (150) may beconfigured to supply power to both ends of power strip (1), therebyensuring that a break (152) in power strip (1) will not result in lossof power to any of robotic devices (20 i, 20 ii, 20 iii, 20 iv). Itshould be noted that while shown in FIGS. 4c and 4 d as electricallyconnected at the ends of power strip (1), power supplies (150, 150 i,150 ii) may alternatively and/or additionally be electrically connectedto any other point or points on power strip (1). That is, in a powerstrip (1) comprising a plurality of electrically interconnected sectionsor segments, power supplies (150, 150 i, 150 ii) may be electricallyconnected to any number of sections anywhere along power strip (1). Itshould also be noted that the power supply redundancy schemes depictedin FIGS. 4c and 4 d are equally suitable for use in the brush and wheelpower distribution system described in detail immediately below.

Referring next to FIGS. 5 through 8a and 8 b, various perspective, sideand cross-sectional views of a robotic device for use in an automatedtape cartridge library having brush and wheel power distribution areshown. Robotic device (20) is supported by a guide rail (2), which isprovided with a pair of oppositely charged power conductors (3),preferably in the form of copper rails. Power rails (3) supply power torobotic device (20) through power transmission carriage assembly (4).Power supplied to robotic device (20) via power rails (3) and powertransmission carriage (4) powers a motor (not shown), which in turndrives belt and gear mechanism (22) to permit robotic device (20) tomove back and forth along guide rail (2) via guide wheels (26). In thatregard, it should be noted that power rails (3) may provide either AC orDC power to robotic device (20). It should also be noted again thatwhile only a single robotic device (20) is depicted, power rails (3) arepreferably suitable, according to any fashion known in the art, toprovide power to multiple robotic devices. As described above inconnection with the brush and stip power distribution, each roboticdevice (20) is suitably equipped with a circuit breaker (not shown) inany fashion known in the art in order to isolate the robotic device (20)from the power rails (3) in the event that the robotic device shortcircuits. In such a manner, the failure of the power rails (3) isprevented.

Power transmission carriage (4) includes multiple cooperating pairs ofconduction wheels (5) (preferably copper), the individual members of acooperating pair provided in contact, respectively, with oppositelycharged conductor rails (3). Conductive brushes (10) are provided tocontact conduction wheels (5) and are spring loaded (11), preferablyindependently, to maintain such contact. To maintain contact betweenconduction wheels (5) and conductor rails (3), power transmissioncarriage (4) also includes vertical pre-load spring (16). Powertransmission carriage (4) still further includes gimbal arm (17) withpivot shaft (18) and pivot screw (9) for carriage compliance. Onceagain, multiple or redundant conduction wheel (5) and conductive brush(10) pairs are preferably provided, and preferably spring loaded (11)independently, to improve robustness and reliability in the event of abrush failure, momentary loss of contact at one or more wheels due toany track irregularities, including seams or joints therein, or voltageirregularities between adjacent power rails (3). In that same regard,while a single vertical pre-load spring (16) is shown, each conductionwheel (5) could also be independently spring loaded to maintain contactwith conductor rails (3), thereby allowing for better negotiation of anytrack irregularities or imperfections, including joints or seams.

The brush and wheel embodiment can reduce particulate generation whichmay accompany the brush and power strip embodiment as a result ofbrushes negotiating imperfectly aligned track joints. Moreover, becauseof the more contained nature of the contact between a brush and wheel asopposed to between a brush and extended power stip, any such particulategeneration can be more easily contained in the brush and wheelembodiment, such as through the use of a container (not shown)surrounding the brush and wheel to capture any particulate.

The brush and wheel embodiment also provides for improved negotiation ofjoints by a robotic device as it provides for wheels rolling rather thanbrushes sliding over a joint. As a result, less strict tolerances arerequired for joint design and assembly. Moreover, a brush passing overan irregularity in a power strip, such as a joint, scrapes both thebrush and the track, causing wear to both. A wheel can more easilynegotiate such irregularities, thereby reducing such wear.

The brush and wheel embodiment also provides for reduced electrical andsliding resistance as compared to the brush and stip embodiment. In thatregard, a beneficial oxide layer that reduces both electrical andsliding resistance develops more easily and quickly between a brush andwheel contact than between a brush and extended power strip contact,again because of the more contained nature of the contact. That is, fora given linear movement of a robotic device, a brush covers much more ofthe surface, and much of the same surface of a wheel than it covers onan extended linear conductive strip. This is particularly advantageousin reducing high brush resistance when the robotic device is travelingat low speeds.

The brush and wheel embodiment also generally reduces the spring loadingforces required. In that regard, because of irregularities in aconductive strip, such as due to joints or seams, a high spring loadingforce is required to ensure contact is maintained between a brush andpower strip, particularly over time as the brush wears. In contrast,with a brush and wheel, there are no irregularities in the point ofcontact between the brush and wheel. As a result, the spring force usedto maintain contact between the brush and wheel can be reduced, whichalso reduces the drive force or power necessary to move the roboticdevice.

Still further, the brush and wheel embodiment also reduces track wear,since the rolling friction between the wheel and track creates less wearthan the sliding friction between a brush and power strip. In thatregard, the conductive strips in a brush and power strip embodiment mustbe made sufficiently thick to allow for wear due to brush contact overtime. Moreover, as previously noted, spring loading forces for brushesin a brush and power strip embodiment must be sufficiently high toensure contact is maintained between the brush and power strip over timeas both wear. A brush and wheel embodiment eliminates these concerns andallows for the use of a more inexpensive track having less stringentdesign and assembly tolerances.

In either of the brush and power strip or brush and wheel embodiments,the power strip or conduction rails may be oriented horizontally, asshown in the Figures, or vertically, or in a combination of both.Indeed, a vertical track orientation may be preferred, particularly forcurved track areas. In that regard, for example, an extended printedcircuit board power strip of the type previously described can be easilybent to follow a curved track area if such a power strip is providedwith a vertical orientation. In contrast, to follow a curved track witha such a power strip oriented horizontally, a curved printed circuitboard may need to be specially manufactured. Moreover, as the radius ofcurvature of a curved track area decreases, skidding and wear of wheelsincreases on a horizontally oriented track. This can be alleviated by avertically oriented track.

For any electrical pickup configuration, the conductors or strips may beprovided in segments or sections that can be electrically connectedtogether in a modular fashion, thereby extending the power conductors orstrip substantially throughout a data storage library. Such sections maybe joined together along the path or a guide rail on which a roboticdevice moves in the library. In that regard, it should be noted that ineither embodiment, the segments or sections of power conductors orstrips may be connected in an end to end fashion to provide for roboticdevice movement in a single dimension, or may be connected in agrid-like fashion to provide for robotic device movement in twodimensions and/or to provide power across multiple horizontal paths forrobotic devices, which paths may be stacked vertically on top of eachother, thereby providing for robotic device access to multiple mediacartridge storage cells arranged in a two dimensional configuration ofmultiple rows and columns, such as a planar “wall” or “floor,” or acurved or substantially cylindrical “wall.” Still further, again ineither embodiment, the segments or sections of power conductors orstrips may be connected in such a fashion as to provide for roboticdevice movement in three dimensions.

When used in such fashions for power distribution, segmented powerstrips will be sensitive to alignment so as not to create a sloppyjoint. A mis-aligned joint in the power strip may cause a brush to losecontact with a power strip due to bounce. Wear on the brushes and powerstrip pieces at the joints may also cause limited life of the joint.

As a result, a joint for such power strips may be pre-loaded andoverconstrained to cause the power strips in the robot guide rail tosubstantially align. Such a joint preferably includes conductorsslightly longer than the supporting structure of the robot guide rail,so as to force adjoining conductors into contact at their ends as guiderails and conductors are assembled. In addition, adjoining ends ofconductors may be beveled or angled such that a force urging theconductors together causes the conductors to slip laterally against eachother, so as to again facilitate alignment at the joint. Such a bevel orangle also spreads out the wiping action of a brush as it traverses thejoint, thereby prolonging the life of the joint and brush, and limitingany problems that may arise as a result of any small offset. Stillfurther, the power strips may be pre-loaded or biased by a spring load,thereby causing the joint to stay in compression for the life of thejoint.

In that regard, referring next to FIGS. 9 through 12a-g, variousperspective, cross-sectional and side views of a power strip and guiderail for use in an automated tape cartridge library are shown. Aspreviously described, power strip sections in a brush and power stripembodiment may be sensitive to alignment. Guide rail sections (2A, 2B)are designed to accept substantially planar, elongated power stripsections (1A, 1B). Power strip sections (1A, 1B) may be of the printedcircuit board type previously described, and may include upper (56) andlower (not shown) copper conductive layers on opposite surfaces of anFR4 type substrate material (58). Track alignment pins (51) and holes(52) in guide rail sections (2A, 2B) ensure that guide rails sections(2A, 2B) are properly aligned at the joint, and a joint bolt (54) isprovided to ensure sufficient force to maintain the joint. In thatregard, an alternative latch mechanism (55) is depicted in FIGS. 11a and11 b to provide sufficient force to maintain the joint.

Power strips (1A, 1B) are preferably beveled or angled (preferably at30°) in a complimentary fashion at adjoining ends so that such ends willmove or slide laterally relative to each other in the X-Y plane duringassembly of the joint, thereby accounting for varying tolerances in thelengths of adjoining power strips (1A, 1B) and/or guide rails (2A, 2B).In that same regard, power strips (1A, 1B) are preferably each providedwith spring arms (60), which act as means for biasing power strips (1A,1B) together against such lateral motion. Spring arms (60) preferablyinclude mounting pin holes (62) formed therein, which are designed toalign with similar mounting pin holes (64) formed in guide rails (2A,2B) for receipt of mounting pins (66). Such a configuration facilitatesthe previously described relative lateral motion between power strips(1A, 1B) in the X-Y plane during assembly, and helps to ensure thatpower strips (1A, 1B) remain in contact after assembly. A similar springarm, mounting pin hole and mounting pin arrangement (67) is preferablyprovided in a central region of each power strip (1) and guide rail (2)section (see FIG. 12e).

Power strips (1A, 1B) are also preferably provided at their adjoiningends complimentary tongue-and-groove like or dove tail type mating edgesor surfaces. Such edges, preferably formed with 45° angles, ensure thatpower strips (1A, 1B) remain co-planer at the joint (i.e., refrain frommovement relative to each other in the Z direction) so as not to exposean edge of an upper (56) or lower (not shown) conductive layer.Electrical connection is provided at the joint through the use of quickconnect electrical slide type connectors (53A, 53B). In that regard,upper (56) and lower (not shown) conductive layers of adjoining powerstrips (1A, 1B) each preferably include an electrical connection point.Upon assembly of power strips (1A, 1B), such electrical connectionpoints are proximate each other such that one connector (3A) creates anelectrical connection between upper conductive layers (56) of adjoiningpower strips (1A, 1B), while the other connector (3B) creates anelectrical connection between lower conductive layers (not shown) ofadjoining power strips (1A, 1B).

In such a fashion, power strips (1A, 1B) are assembled to create a jointwhere their respective conductive layers are proximate such that arobotic device having brush or wiper type contacts as previouslydescribed maintains electrical contact therewith as the robotic devicetraverses the joint. A well aligned power strip and guide rail joint isthus provided which facilitates easy movement of a brush or wipercontact thereacross, while at the same time accounting for differingmanufacturing tolerances and expansion rates between the dissimilarmaterials used in the power strips (1) and guide rails (2). It shouldalso be noted that while depicted in the figures in conjunction withprinted circuit type power strips (1), such features may be used withany type of power strip (I) previously described, or with any other typeof joint for power conductors, such as a single conductive strip or busbar. Indeed, many of the above features may also be used with any typeof joint, such as between guide rails without power.

As is well known in the art, robotic devices in an automated tapecartridge library must be able to communicate with a host controller.This is typically done using multiple conductors (three or more)including power, ground, and signal(s), which can cause many of the samecabling problems previously described. The relatively high cost and lowreliability of conductors and connectors pose a problem for implementinghigh reliability, low cost automated robotic data storage libraries.Such a problem is particularly troublesome if the space available forrouting such conductors is limited.

Such problems can be overcome by using the oppositely charged conductivelayers of a power strip, power rails, or a cable pair to supply not onlypower to the robotic devices, but communication signals between therobotic devices and a host controller as well. In that regard, in abrush and power strip embodiment, multiple conductors are particularlyproblematic when power and communication signals need to be sent torobotic devices via the power strip and brushes. Since the reliabilityof the electrical connections in such an embodiment is inherentlyrelatively low, a substantial reliability and complexity penalty may beincurred when multiple conductors are used.

According to the present invention, a smaller, lower cost and higherreliability system is made possible by eliminating all conductors exceptthose absolutely needed: power and ground. Information which wouldotherwise be communicated via dedicated signal conductors is insteadmodulated onto the power conductor. In such a fashion, the communicationsignals share the same conductor that is used to power the roboticdevice. Modulator circuits on a host controller and the robotic devicesencode the data from the eliminated conductors and impress a modulatedsignal onto the power conductor. Demodulator circuits on both endsreceive and recover the communication signals, translating the data backinto its original form. High-speed full-duplex communication is thusimplemented without the need for more than two conductors connecting thehost controller and the remote robotic devices.

Referring now to FIG. 13, a simplified block diagram illustratingdistribution of communication signals to and from robotic devices (72,74) for use in an automated tape cartridge library is shown. As seentherein, a power supply (70) provides power to robotic devices (72, 74)via power and ground conductors (76, 78), which are preferably theoppositely charged conductive layers of a power strip as described indetail above. A host controller (80), using processor and logic circuits(82), generates signals for use in controlling the movement andoperations of robotic devices (72, 74). Host controller (80) is alsoprovided with modulator/demodulator circuitry (84) to encode suchcommunication signals and impress or superimpose such signals onto thepower signal provided to the robotic devices (72, 74) via the powerconductors (76, 78). Similar modulator/demodulator circuitry (84) isprovided onboard robotic devices (72, 74) to recover and decode thesignals from host controller (80). Once recovered and decoded, suchsignals are transmitted to motion controller circuitry (86) onboardrobotic devices (72, 74) in order to effect the desired movement andoperation of the robotic devices (72, 74).

Robotic devices (72, 74) communicate with host controller (80) in thesame fashion, thereby providing feedback to the host controller (80)concerning movement and operation of the robotic devices (72, 74), whichinformation the host controller (80) may use to generate further controlsignals. In that regard, such communication signals may be combined withthe power signal in any fashion known in the art. For example, becausepower signals are typically lower frequency signals, communicationsignals may comprise higher frequency signals so that the power signalmay be filtered out by robotic devices (72, 74) and host controller (80)using high-pass filters to thereby recover the communication signals. Insuch a fashion, high-speed full duplex communication may be implementedbetween the host controller (80) and robotic devices (72, 74) withoutthe need for multiple conductors, cabling, or wireless connection.

Electromagnetic interference and unintended signal emissions can be aproblem when transmitting communication signals between robotic devicesand a host controller using the oppositely charged conductive layers ofa power strip as described above. This can be particularly true forpower conductors that are quite long. Interference from radio,television, and other radio frequency (RF) electromagnetic radiationsources, whether or not intentionally emitted, can interfere with thecommunication signals modulated onto the power conductors. Suchinterference can cause data transmission errors and slow the maximumattainable rate of data transfer.

In that same regard, when communication signals are modulated onto along power conductor, some of the RF energy can radiate through the airand interfere with nearby independent power conductors. If the nearbypower conductors also contain modulated communication signals, harmfulinterference can result. The energy radiated by the modulated powerconductors may also cause interference in radio and television broadcastbands, or other restricted RF bands. Such interference may be prohibitedby government regulations.

According to the present invention, the electromagnetic compatibility(EMC) of the brush and power strip embodiment of the present inventionis improved by the orientation of the power strip conductors. As will bedescribed in greater detail below, positive and negative (ground)conductors are preferably separated by a thin layer of insulatingdielectric. The positive conductor is preferably centered over thenegative conductor. The negative conductor is preferably made wider thanthe positive conductor in order to minimize fringing of the electricfiled due to the modulated communication signal. The thin dielectricminimizes the “loop area” of the conductors. The conductors themselvesare flat and relatively thin in order to reduce their respective surfaceareas, thereby reducing “skin effect.” All of the above features serveto improve the EMC of the brush and power strip embodiment.

Referring next to FIGS. 14 and 15, cross-sectional and top views of thepower strip for use in an automated tape cartridge library are shown. Asseen therein, one conductive layer (56), which is shown in the figuresas positively charged or a power conductor, is preferably provided witha narrower width, w₁, than the width, w₂, of the other conductive layer(57), which is shown in the figures as negatively charged or a groundconductor. A thin dielectric material (58) is provided betweenconductive layers (56, 57), and has a width, w₂, that is preferablysubstantially equal to that of conductive layer (57). While notrequired, conductive layer (56) is preferably centered on the surface ofone side of dielectric material (58), at equal distances, x, from theedges of dielectric material (58). In that regard, as previouslydescribed, conductive layers (56, 57) are preferably copper. Dielectricmaterial (58) preferably has a low dielectric constant, k, such as FR4previously described, or Teflon.

The above-described configuration serves to improve the electromagneticcompatibility (EMC) of the power strip. More particularly, the differentwidths of the conductive layers (56, 57) helps to minimize fringing ofthe electric field due to the modulated communication signals. In thatregard, the greater the distance x can be made, either by narrowingconductive layer (56) or by widening conductive layer (57) anddielectric (58), the greater the beneficial effect on fringing.Conductive layers (56, 57) should, however, maintain sufficient width toallow adequate contact with brushes (6) in order to supply power to arobotic device.

Moreover, as is well known in the art, electrical current is generallyforced to the outside surfaces of a conductor, particularly at higherfrequencies. Conductors having less surface area therefore have higherresistance, a phenomenon generally referred to as “skin effect.” Bymaking conductive layers (56, 57) generally flat and thin, more surfacearea is created, thereby reducing resistance for the higher frequencycommunication signals. Such lowered resistance in turn reduced signalloss, thereby allowing for the use of longer tracks, while at the sametime improving signal integrity by providing better immunity frominterference by other signals.

Still further, a thin dielectric (58) helps to minimize the “loop area”of the conductors (56, 57). In that regard, FIGS. 16a and 16 b are across-sectional view and a simplified electrical schematic,respectively, of the power strip for use in an automated tape cartridgelibrary. As seen therein, conductors (56, 57) are connected through apower supply (90) and a load (92), thereby creating a loop. While thelength, 1, of conductors (56, 57) is generally fixed, the thickness, t,of the dielectric (58) therebetween may be adjusted. That is, while thelength of the loop is generally fixed, its height is adjustable. A thindielectric (58) thus helps to reduce “loop area.”

As previously noted, by minimizing fringing, “skin effect” and “looparea,” the above-described configuration improves electromagneticcompatibility (EMC). In general, the above-described power rail presentsa low impedance, thereby reducing coupling from interfering signals. Inparticular, minimizing fringing reduces the possibility that acommunication signal on a power rail will interfere with other devices,including other power rails carrying other communication signals.Minimizing “skin effect” and “loop area” also reduces the possibility ofsuch radiation type interference.

In a power line communication system such as described above, signalreflections can pose a significant signal integrity problem. Reflectionscan destructively interfere with the communication signal, particularlywhen the length of the power line is long compared to the wavelength ofthe carrier signal. The reflection problem can be mitigated with theaddition of line terminators at the extreme ends of the power line. Inthat regard, FIG. 17 is a simplified electrical schematic diagramillustrating a termination scheme for a line in a power strip or railcommunication system according to the present invention. As seentherein, the termination scheme comprises two parallel terminators (100,101) at each of the two ends of the power line/rail (102). As shown inFIG. 17, each terminator (100, 101) preferably comprises an RCtermination, although those of ordinary skill will appreciate that avariety of termination schemes could be employed to achieve the sameeffect.

Still referring to FIG. 17, series terminators (93, 94), which arepreferably resistors, are also preferably provided on the output of eachmodulator circuit (95) for both the host controller (96) and theautomated robot, or handbot (97). The combination of series terminationand parallel termination further enhances the signal integrity of thepower line (102). Either series or parallel termination could be used onits own, however. Proper line termination such as that depicted in FIG.17 dramatically improves signal integrity and increases the maximumattainable rate of data transfer as well as extending the maximum lengthof the conductors.

Referring now to FIG. 18, a schematic diagram illustrating a system fordetecting brush failure is shown. A mechanism, shown generally by (200),moves along first conductor (202) and second conductor (204) in adirection indicated by (206). Mechanism (200) may be, for example,robotic device (20) for use in a data storage library. Mechanism (200)draws power for operation from one or both of first conductor (202) andsecond conductor (204). During normal operation, first brush (208) andsecond brush (210) conduct currents i₁ and i₂, respectively, fromconductor (202). Similarly, third brush (212) and fourth brush (214)conduct currents i₃ and i₄, respectively, to conductor (204). Brushes(208, 210, 212, 214) may contact conductors (202, 204) directly or maybe members of a pickup assembly containing other elements which directlycontact conductors (202, 204). In the embodiment shown, currents i₁ andi₂ form a parallel path supplying positive supply (216). Likewise,currents i₃ and i₄ form parallel paths for negative supply (218).Positive supply (216) and negative supply (218) may be, for example, 48volts and return.

First current sensor (220) detects first current i₁, from brush (208)and generates first current signal (222). Similarly, second currentsensor (224) senses second current i₂ from brush (210) and generatessecond current signal (226). Third current sensor (232) senses thirdcurrent i₃ from brush (212) and generates third current signal (234).Fourth current sensor (236) senses fourth current 14 through brush (214)and generates fourth current signal (238). Differencer (240) generatesnegative current difference signal (242) as the difference between thirdcurrent signal (234) and fourth current signal (238). Circuitry (244)accepts one or more signals indicative of brush operation, such aspositive current difference signal (230), negative current differencesignal (242), third current signal (234), fourth current signal (238),and the like. Circuitry (244) generates output signal (246) indicativeof the operating status of brushes (208, 210, 212 and 214). For example,circuitry (244) may compare one or both difference signals (230, 242)with a threshold. If the threshold is exceeded, circuitry (244)indicates a brush anomaly. If difference signal (230, 242) is signed,circuitry (244) determines the problematic brush based on the sign ofdifference signal (230, 242). For the example shown in FIG. 18, anegative difference (230) would indicate problems with second brush(210) and a positive difference signal (230) would indicate problemswith first brush (208). If difference signal (230, 242) is not signed,examining current signals (238, 234) will indicate which brush (214,212) is having difficulties. In addition, feeding current signals (238,234) into circuitry (244) permits circuitry (244) to determine multiplebrush failures if the combined current draw is too low.

Referring now to FIGS. 19a through 19 d, schematic diagrams illustratingcircuitry for detecting brush failure are shown. In FIGS. 19a and 19 b,each current sensor (220, 224, 232, 236) is implemented using a 0.03 Ω,1 W resistor placed in series with the current to be detected. As willbe recognized by one of ordinary skill in the art, other current sensorsmay be utilized in the present invention.

With reference to FIG. 19a, resistor (220) is placed in series withbrush (208) to sense current i₁. Each side of resistor (220) is tappedby conversion circuit (250) which converts the voltage drop acrossresistor (220) into a proportional output current as first currentsignal (222). Similarly, resistor (224) is placed in series with brush(210) to measure second current i₂. Conversion circuit (252) measuresthe voltage drop across resistor (224) and generates a proportionalcurrent as second current signal (226). The voltage inputs of conversioncircuit (250) are reversed relative to corresponding inputs onconversion circuit (252). Thus, if first current i₁ is the same assecond circuit i₂, first current signal (222) will cancel second currentsignal (226). If first current i₁, is different than second current i₂,a proportional difference will appear between first current signal (222)and second current signal (226). This difference current will flowthrough resistor (254) creating a difference voltage. Buffer circuit(256) buffers this difference voltage to produce positive currentdifference signal (230, labeled as 48V_BRUSH_FB). Thus, resistor (254)and buffer circuit (256) are functioning as differencer (228).

With reference to FIG. 19b, resistor (232) is placed in series withbrush (212) to sense current i₃. The voltage drop across resistor (232)is detected by buffer circuit (258) to generate third current signal(234, labeled as 48V_RTN_BRUSHA-FB). Similarly, resistor (236) is placedin series with brush (214) to sense current i₄. Buffer circuit (260)senses the voltage drop across resistor (236) and generates fourthcurrent signal (238, labeled as 48V_RTN_BRUSHB_FB).

Referring now to FIGS. 19c and 19 d, positive current difference signal(230), third current signal (234) and fourth current signal (238) arereceived by analog-to-digital converter (270). Other analog signals tobe converted, indicated by (272), are also received by analog-to-digitalconverter (270). Select inputs, indicated by (274), determine whichinput to analog-to-digital converter (270) will be digitized. Thedigitized value appears on bus (276). Bus (276) is read by amicroprocessor, not shown for clarity. This microprocessor carries outthe assessment of brush health as described above. In this example,negative current difference signal (242) is calculated by themicroprocessor using digitized versions of third current signal (234)and fourth current signal (238).

Referring now to FIG. 20, a schematic diagram illustrating power stripfault detection through current sensing by the robotic device is shown.One or more conductors (202, 204) may contain a defect, indicated by(280). Defect (280) may be caused due to joint breakdown, mechanicaldamage of a conductor, age, wear, and the like. The effect of defect(280) is to degrade the ability of power supply (282) from supplyingpower along conductors (202, 204). In addition, communications travelingalong conductors (202, 204) may be impeded. Defect (280) may appear asan increase in the impedance of conductor (202, 204) including acomplete break or infinite impedance at defect (280). Defect (280) canbe detected by examining the power drawn from one or both conductors(202, 204) on either side of defect (280).

In the embodiment shown in FIG. 20, power is indicated by measuringcurrent. First current sensor (220) is implemented with a currentsensing loop generating first current signal (222). Similarly, secondcurrent sensor (224) is implemented with a current sensing loopgenerating second current signal (226). Differencer (228) generatescurrent difference signal (230) indicative of the difference in powersensed on either side of defect (280).

Referring now to FIG. 21, a schematic diagram illustrating power stripfault detection through voltage sensing by the robotic device is shown.Voltage sensor (290) is inserted to measure the voltage potentialbetween the path taken by current i₁ and the path taken by current i₂.Similarly, voltage sensor (292) is inserted to measure the voltagepotential between the path for current i₃ and the path for current i₄.Construction of voltage sensors (90, 92) is well known in the art.Measuring the voltage difference between paths fed by brushes (208, 210)or by brushes (212, 214) provides an indication of the difference inpower being supplied through each brush pair.

Referring now to FIG. 22, a schematic diagram illustrating power stripfault detection through impedance sensing by the robotic device isshown. Defect (280) in one or more conductor (202, 204) may be detectedby directly measuring the impedance of conductor (202, 204). Theembodiment shown measures the impedance of conductor (202). A similarscheme may be used to measure the impedance of conductor (204). Also, inthe embodiment shown, the same brushes (208, 210) used to supplypositive supply (216) are used for measuring impedance of conductor(202). Alternatively, a separate set of brushes or other type of pickupmay be used.

Signal generator (300) generates a time-varying signal which is sentthrough brush (210) onto conductor (202). In the embodiment shown, thistime-varying signal is induced onto cable (302), connected to brush(210), by coil (304). Preferably, at least one parameter of thetime-varying signal is controlled by control logic (306). Controllableparameters include frequency, amplitude, signal type, duration, and thelike. The time-varying signal is carried through conductor (202),through brush (208) and is detected by sensor (308) which detectscurrent flowing in cable (310) connected to brush (208). Sensor (308)generates signal (312) indicative of impedance. Control logic (306)generates health signal (314) based on received signal (312).

One method by which control logic (306) determines the presence ofanomaly (208) in conductor (202) is by comparing signal (312) to one ormore thresholds. For example, if anomaly (280) is a complete break, nosignal (312) will be received.

Another means by which control logic (306) can determine the health ofconductor (202) is to base the decision on a reference impedance valuetaken when conductor (202) was fully operational. For example, areference impedance may be measured following initial checkout. Thisreference impedance may be stored by control logic (306) or elsewhere.During operation, control logic (306) calls up the reference impedancevalue and compares the reference impedance against measured impedance todetermine the presence of any defect (280). Control logic (314) may alsotransmit a measured impedance for comparison elsewhere.

It should be noted that any of the techniques described with regard toFIGS. 18-22 may be used for either determining brush health or conductorhealth. This is due to the fact that a brush condition will appear thesame at any position along the track. In contrast, defect (280) in aconductor occurs at a localized position along the track. Thus, anyproblem which is determined and then disappears as mechanism (200)travels along rail (2) indicates a defect (280). This defect can beconfirmed by moving mechanism (200) back over the suspected area. Abrush defect, even one that appears intermittently, will not appear inthe same manner at a particular geographic location. The circuitryillustrated in FIGS. 19a-19 d may be readily adapted to any of the abovetechniques.

Referring now to FIG. 23, a schematic diagram illustrating track faultdetection by impedance measurement is shown. Signal generator (320)generates a test voltage across conductors (202, 204). This test voltageis affected by controller (322) which may control the voltage amplitude,time-varying properties such as signal shape and frequency, duration,and the like. Sensor (324) located away from generator (320) detects thetest voltage and generates sensed signal (326) in response thereof.Transmitter (328) sends an indication of sensed signal (126) tocontroller (322). This transmission may occur over one or both ofconductors (202, 204), through cabling (not shown), through a wirelesslink, or the like. Controller (322) then determines the impedance ofconductors (202, 204) based on the voltage sent by generator (320) andthe voltage as received by sensor (324).

Mechanism (200) may be used to pinpoint the location of any defect inconductors (202, 204). Sensor (330) receives the test voltage throughpickups (332, 334) following conductors (202, 204), respectively. Sensor(330) generates signal (336) indicative of the sensed test voltage.Transmitter (338) transmits a signal based on sensed signal (336) tocontroller (332) through one or both of pickups (332, 334), throughseparate cabling, through a wireless link, or the like. In theembodiment shown, switch (340) is connected to transmitter (338) fortransmitting through pickup (332) to controller (322). Transmitter (338)also transmits the position of mechanism (200) along conductors (202,204). In this manner, controller (322) can determine the location of anydefect in conductors (202, 204).

Referring now to FIG. 24, a schematic diagram illustrating embodimentsof track fault detection by signal transmission is shown. Transmitter(350) transmits a test signal onto one or more conductors (202, 204).This test signal may include a temporary surge in current, atime-varying analog signal, a digital signal, or the like. Receiver(352), located at an opposite end of conductor (202, 204) receives thetest signal and responds back to transmitter (350). This response may besent through one or more of conductors (202, 204), may be sent throughseparate cabling (not shown), may be sent over a wireless link, or thelike. Transmitter (250) then determines the health of conductor (202,204) based on the received signal. Transmitter (350) may also wait for atimeout period after transmitting a signal onto conductor (202, 204).Transmitter (350) determines an anomaly on conductor (202, 204) if noresponse is received from receiver (352) within the timeout period.

Mechanism (200) may be used to pinpoint any defect on conductors (202,204). Receiver (354) traveling down conductor (202, 204) in mechanism(200) receives the test signal through pickup (332). Receiver (354) thentransmits back to transmitter (350) through conductor (202, 204),through separate cabling, through a wireless link, or the like.

Referring now to FIG. 25, a schematic diagram illustrating analternative embodiment of track fault detection by signal transmissionis shown. In this embodiment, mechanism (200) includes pickups (332,334) interconnected by connection (360). Pickups (332, 334) are spacedapart in direction of travel (206) of mechanism (200) along conductor(202, 204). Thus, when mechanism (200) is over a defect in conductor(202, 204), a path formed by pickup (332), connection (360) and pickup(334) shorts around the defect. This allows a test signal inserted ontoconductor (202, 204) by transmitter (350) to be more readily received byreceiver (352). When mechanism (200) moves away from the defect, thetest signal will be attenuated or not receivable by receiver (352).Transmitter (350), knowing tic position of mechanism (200), candetermine the location of a defect in conductor (202, 204) based onreceiving a transmission from receiver (352).

Referring now to FIG. 26, a schematic diagram illustrating track faultdetection with a plurality of signal transmitters is shown. A pluralityof transmitters, indicated by (370 i-n) are spaced along conductor (202,204). Each transmitter (370 i-n) is under the control of controller(372). Controller (372) instructs one transmitter (370 i-n) to insert atest signal onto conductor (202, 204). Receiver (374) receives the testsignal and forwards an indication of the test signal to controller(372). By sequencing through transmitters (370 i-n) for transmission ofa test signal, controller (372) can determine the segment of track whichcontains a defect.

Referring now to FIG. 27, a schematic diagram illustrating track faultdetection with a plurality of signal receivers is shown. Transmitter(380) transmits a test signal onto conductor (202, 204). A plurality ofreceivers (382 i-n) are located along conductor (202, 204). Eachreceiver (382 i-n) transmits a signal indicative of the received testsignal to transmitter (380). By examining the signals received fromreceivers (382 i-n), transmitter (380) can determine the location of adefect along conductor (202, 204).

As will be recognized by one of ordinary skill in the art, any of theabove methods for detecting track fault may be combined to produce amore robust fault detection system.

Referring now to FIG. 28, a schematic diagram illustrating rail anomalyrecovery according to an embodiment of the present invention is shown.Anomaly (280) in one or more conductor (202, 204) may prevent power frompower supply (282) from extending beyond anomaly (280). In this case,robotic device (20 i) located beyond anomaly (280) will be cut off frompower supply (282). This may render robotic device (20 i) inoperative.

This problem may be remedied by moving a second robotic device,indicated (20 ii), over defect (280) in conductor (202, 204). Currentflows along conductor (202), into brush (208), through conductive path(380), out brush (210) and onto conductor (202) separated by defect(280). Similarly, current flows through separated section of conductor(204), into brush (214), through conductive path (382), out of brush(212) and onto conductor (204) before defect (280). In this case, brush212, conductive path 282 and brush 214 are constructed as a wideconductor capable of bridging defect 280. This wide conductor may beimplemented as a single, wide conductive brush or bar.

This provides yet another method of detecting anomaly (280) in conductor(202, 204). As robotic device (20 ii) moves along conductor (202, 204),the point at which robotic device (20 i) becomes operative indicates thelocation of defect (280). The location of defect (280) can then bestored in memory. Any robotic device (20) can then be moved back to thelocation of defect (280) to provide power to decoupled conductorsections (202, 204).

In another embodiment of the present invention, brushes (208, 210) are asingle wide conductor capable of spanning defect (280), eliminating theneed for conductor 380 between brushes 212, 214.

Referring now to FIG. 29, an illustration of a linear data storagelibrary with a graphical display is shown. Storage library (390)includes a plurality of horizontal tracks (392). Robotic devices (20)travel along horizontal tracks (392) to access media storage locationsand media access devices. Storage library (390) also includes severalelevators (394) transporting robotic devices (20) between horizontaltracks (392).

Storage library (390) also includes graphical display (396) having aplurality of display elements (398). Each display element (398)represents one rail segment. Each rail segment may be a singlehorizontal track (392) or elevator (394). Rail segments may also includesections of a horizontal track (392) or elevator (394). These sectionsmay be physical divisions of tracks (392) and elevator (394), such assections between joints or levels, or may be logical divisions createdfor ease of display or to otherwise logically divide tracks (392) andelevators (394). Each display element (398) is positioned relative toother display elements (398) to reflect positioning of correspondingtracks (392) and elevators (394) within data storage library (390).Display (396) is updated based on data generated to describe the use ofeach track (392) and elevator (394).

Various conditions may be displayed. These include mechanical condition,electrical condition, communication status, temperature, ease of use,and distance traveled by robotic devices (20) for each track (392),elevator (394) or segment thereof.

Referring now to FIG. 30, an illustration of a data storage library withcurved tracks is shown. Storage library (410) includes a plurality oftracks (412) which extend along one side, curve to extend across thelibrary and then extend along the other side. A plurality of roboticdevices (20) run along tracks (412). Storage library (410) also includesseveral elevators not seen in this view. Storage library (410) furtherincludes a plurality of media access devices for reading data from andwriting data to media held within library (410).

Referring now to FIG. 31, an illustration of a curved track data storagelibrary with a graphical display is shown. Storage library (410)includes graphical display (396) showing one or more tracks (412)displayed as track segments, one of which is indicated by (420). Tracksegments (420) are arranged on graphical display (396) to correspondwith the actual positions of the portions of track represented by eachtrack segment (420) inside of library (410). The example shown in FIG.31 illustrates a single track (412) with eleven track segments (420).Track designation (422) indicates which track (412) is displayed.Virtual meter (424) indicates the current drawn from conductors runningalong track (412). Various symbols are located on or near track segments(420) to indicate status such as, for example, position of roboticdevice (426), electrical fault indicator (428), communications faultindicator (430), and the like.

Referring now to FIG. 32, a graphical display for a multi-track datastorage library is shown. Graphical display (396) allows all tracks(412) in library (410) to be displayed simultaneously. Representation oftracks are displayed to reflect the relative positions of these trackswithin library (410). Symbols displayed on display (396) include tracksymbols (440), track segment symbols (420), robotic device positions(426), elevator symbols (442), temperature range error symbols (444),status check in progress symbols (446), condition unknown symbols (448),and the like. Heartbeat symbols (450) indicate system components aregenerating regular heartbeat signals. These typically includecommunication links. Access device indicators (452) indicate the statusof media access devices.

Referring now to FIG. 33, a block diagram illustrating a data storagesystem with track-based status monitoring is shown. A data storagesystem, shown generally by (460), includes a plurality of tracks (462)with each track (462) divided into a plurality of segments (464).Segments (464) may correspond with physical divisions such as, forexample, track joints, or may be logical designations to assist ingathering or displaying status information. Robotic devices (20) travelalong tracks (462) to transport data storage media. Typically, eachtrack (462) has one or more power supply (466) supplying power torobotic devices (20). Each track (462) may also include communicationlink (468, corm link) in communication with robotic devices (20) andother means for determining the status of segments (464) as providedabove. Communication links (368) are in communication with controller(470). Controller (470) controls the operation of each robotic device(20) and receives information about the status of each segment (464)through communication link (468). Server (472) interfaces database (474)with controller (470). Database (472) includes information about eachsegment (464). Database (474) is updated by controller (470) on the useof each segment (464) by robotic devices (20). Management processor(476) also accesses database (474) through server (472). Managementprocessor (476) generates data describing the use and status of eachrail segment (464). This information is displayed by managementprocessor (476) on display (396).

Database (474) may contain a variety of additional information. Forexample, database (474) may contain impedance values taken for eachtrack segment (464) when that segment (464) was known to be operational.Database (474) may also contain locations of known anomalies alongtracks (462). Various thresholds for determining the health of elementswithin data storage system (460) may also be held in database (474).While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed is:
 1. A method of monitoring status in a data storagelibrary having a plurality of robotic devices traveling on rails withinthe data storage library, each robotic device operative to access aplurality of data storage devices, the method comprising: dividing therails into a plurality of rail segments; establishing a databasecomprising information about each rail segment; updating the databasebased on use of each rail segment by robotic devices; and generatingdata describing the use of each rail segment.
 2. A method of monitoringstatus in a data storage library as in claim 1 further comprising:generating a display having a plurality of display elements, eachdisplay element representative of one rail segment; positioning eachdisplay element relative to other display elements in the display toreflect positioning of corresponding rail segments within the datastorage library; and updating the display based on data generated todescribe the use of each rail segment.
 3. A method of monitoring statusin a data storage library as in claim 1 wherein generating datacomprises determining a mechanical condition of each rail segment.
 4. Amethod of monitoring status in a data storage library as in claim 1wherein generating data comprises determining an electrical condition ofeach rail segment.
 5. A method of monitoring status in a data storagelibrary as in claim 1 wherein generating data comprises determiningdistance of robotic device travel along each rail segment.
 6. A methodof monitoring status in a data storage library as in claim 1 whereingenerating data comprises determining ease of travel of robotic devicesalong each rail segment.
 7. A data storage library comprising: aplurality of storage locations for holding data storage media disposedwithin the library; at least one rail disposed within the library, eachrail located to provide access to storage locations, each rail logicallydivided into at least one rail segment; at least one robotic devicemounted to travel along each rail, the robotic device accessing storagemedia held in the storage locations; a database holding operationalstatus information about the data storage library, the informationarranged according to rail segment; a graphical display for displayingthe condition of each rail segment as a graphical element, eachgraphical element positioned on the display relative to other graphicalelements so as to have the same logical relationship as the position ofthe rail segment corresponding to the graphical element relative to railsegments corresponding to other displayed graphical elements; andcontrol logic in communication with each rail, each robotic device, thedatabase and the graphical display, the control logic operative to (a)monitor an operating condition of each rail segment, (b) record theoperating condition of each rail segment in the database, (c) determinean operating fault with any rail segment, and (d) update the displaybased on the determined operating fault.
 8. A data storage library as inclaim 7 wherein the graphical display is further operative to displaythe location of each robotic device.
 9. A data storage library as inclaim 7 further comprising at least one data storage access device foraccessing data stored on storage media, the graphical display furtheroperative to display the operational status of at least one data storageaccess device.
 10. A data storage library as in claim 7 wherein eachgraphical element displays a mechanical health of the rail segmentcorresponding to the graphical element.
 11. A data storage library as inclaim 7 wherein each graphical element displays an electrical health ofthe rail segment corresponding to the graphical element.
 12. A datastorage library as in claim 7 wherein each graphical element displays anindication of the amount of robotic device travel on the rail segmentcorresponding to the graphical element.
 13. A data storage library as inclaim 7 wherein each graphical element displays an indication of theease of robotic device travel on the rail segment corresponding to thegraphical element.
 14. A method of diagnosing the condition of anautomated data storage library comprising: determining the location ofeach robotic device operating within the library; determining a railsegment supporting each robotic device based on the determined location;accumulating usage information of each determined rail segment;recording the usage information associated with each rail segment; anddetermining usage alarms based on the accumulated usage information. 15.A method of displaying the status of an automated data storage librarycomprising: dividing each rail upon which robotic devices travel intorail segments; receiving a request to display at least one rail;generating graphical symbols for rail segments comprising each requestedrail; displaying the rail segment graphical symbols on a display screenso as to create a logical representation of each requested rail; anddisplaying on the display screen an indication of the status of eachrail segment comprising each requested rail.
 16. A method of displayingthe status of an automated data storage library as in claim 15 furthercomprising: determining that a problem has occurred on a rail segment;automatically displaying the rail segment graphical symbols for the railincluding the rail segment with the operational problem; andhighlighting the rail segment graphical symbol corresponding to the railsegment with the operational problem.
 17. A method of monitoring statusof an automated data storage library comprising: correlating operationof each robotic device within the data storage library to a guide railsegment currently supporting the robotic device; and mapping reliabilitystatistics generated from robotic device operation to each guide railsegment.
 18. A method of monitoring status of an automated data storagelibrary as in claim 17 further comprising displaying the reliabilitystatistics on a display screen, each reliability statistic displayed inassociation with a display of the guide rail segment with which thereliability statistic is mapped.